1. Field of the Invention
The invention relates to a magnetic stimulating apparatus which applies a magnetic field to a living body to generate eddy currents to treat health disorders such as, urinary incontinence.
2. Related Art
For example, the treatment of urinary incontinence based on magnetism is conducted in the following manner. A pulsative magnetic field of a magnetic flux density of 0.01 to 3 teslas, a repetitive frequency of about 1 to 100 Hz, and a pulse width of about 100 .mu.s to 1 ms is continuously applied to the pudendum or the waist for about 15 minutes, thereby generating eddy currents.
As described in Examined Japanese patent publication HEI 3-67423, for example, such a magnetic field is generated by repeatedly supplying a pulsative large current to a coil.
A pulsative magnetic field due to a coil is generated by applying a DC voltage V to a capacitor to store charges, switching a thyristor to convert the energy W.sub.1 =CV.sup.2 /2 (where C is the capacitance of the capacitor) stored in the capacitor into a pulse current, and by supplying the pulse current to the coil. In order to generate a large pulsative magnetic field, therefore, countermeasures: (1) C and V are increased; and (2) the inductance L of the coil is increased must be taken.
When the inductance L of a coil is increased, however, also the resistance R of the coil is increased, with the result that a large amount of heat W.sub.2 =i.sup.2 R/2 is generated by a large current i and the increased resistance R. In this way, in the method in which a magnetic field for stimulating a living body is generated from a coil, most of the supplied energy is dissipated as heat, resulting in a large power loss. In the method, therefore, the efficiency of generating a magnetic field is poor and a large power (several hundreds watts) is required. The generated heat is not used in the treatment. During the treatment which is continuously conducted for about 15 minutes, such heat may cause bum or impede the stable operation of the apparatus. In the case of the treatment of stress incontinence, particularly, since a high repetitive frequency (50 Hz) must be used, the heat loss is large. As a result, a large amount of energy must be replenished and hence continuous stimulation is hardly conducted by using a usual commercial power source.
When magnetism is to be generated for a long period by the method, a large cooling equipment is inevitably required, resulting in that the whole size of the apparatus is greatly enlarged. Such an apparatus occupies a large space in a treatment room, so that works for treatment is impeded. In the method, furthermore, the capacitor and the coil are bulk and large currents are supplied to them. Therefore, loud noises are produced in a treatment room by vibration of the capacitor or the coil.